Technical Abstract: Development of plant-based, fish-meal free, aquaculture feeds will provide economic, environmental, and health benefits to several sectors of society. Fish growth and feed costs need to be competitive with that observed using current formulations. New ingredients that have not been routinely fed to trout will be tested in the future, but a fish meal free feed using currently available ingredients is needed in order to measure improvements in formulations over time. High protein, purified plant products that have had many of the anti-nutrients removed are available but are more expensive than the more common ingredients. Higher nutrient density feeds (45% protein, 20% fat) are being fed in increasing amounts in the U.S. trout industry relative to the standard feeds (40% protein, 15% fat). A study was conducted to evaluate the effect of protein source and nutrient density on fish growth, feed efficiency, digestibility and plasma amino acid concentrations. A four by two factorial treatment arrangement with four protein sources (fishmeal/barley, plant concentrates, plant meals, animal and plant/ no fish) and two nutrient densities was used. Six of these feeds are fish meal free. Two additional control feeds were fed, a commercial fish-meal trout feed and a fish meal/wheat flour feed. Rainbow trout (House Creek strain, College of Southern Idaho; approximately 20 g initial weight) cultured in 145-L liter fiberglass tanks (50 fish/tank; 3 tank/diet) in a fresh water flow through system (spring water, 14.5ºC at 4L/min) were fed the test diets fed by hand to satiation for 12 weeks. At termination, 10 fish/tank were sampled for determination of proximate composition and blood from 5 fish/tank was collected for determination of amino acid concentrations.